Anti-icing arrangements for heat exchangers of air condensing apparatus



April 20, 1965 HELLER ET AL 3,179,164

ANTI-ICING ARRANGEMENTS FOR HEAT EXCHANGERS OF AIR CONDENSING APPARATUSFiled May 8, 1962 2 Sheets-Sheet 1 INVENTORS' (6710 HELLER 4195140 FaRGOBY 64am raucsmvf/ Jar-t9:

A ril 20, 1965 L. HELLER ET AL 3,179,164

ANTI-ICING ARRANGEMENTS FOR HEAT EXCHANGERS OF AIR CONDENSING APPARATUSFiled May 8, 1962 2 Sheets-Sheet 2 INVENTORS LflszLa #ELLE/Q BY 95240P01960 6/7/80? ToMcsnl/ll United States Patent 3,179,164 ANTl-ICHJGARRANGEMENTS FOR EEAT EXCHANGERS 0F Am CQNDENSlNG APPARATUS LaszloHeller, Laszlo Fargo, and Gabor Tomcsanyi, Budapest, Hungary, .assignorsto Licencia Talalmanyokat Ertekesito Vallalat, Budapest V, Hungary, afirm Filed May 8, 1962, Ser. No. 193,133 Claims priority, applicationHungary, May 10, 1961, IE 385 7 Claims. (Cl. 165-71) and feeds it to thesurface heat exchanger, where the relatively hot withdrawn water iscooled by the action of atmospheric air, and the thus cooled Waterisreturned by the pressure reducing apparatus to the mixing condenser.In the latter it is admixed with steam entering the mixing condenser, asfrom the exhaust of a steam turbine, and thereby reheated.

Air condensing units of this type are used in conjunction with steamturbines of steam power plants, and are so designed that they caneffectively cool the cooling Water, at relatively high summertemperatures and under full load, to a temperature suitable for thesteam turbine operation.

A heat exchange surface which is adequately sufficient for cooling ofthe Water at relatively high summer temperature and at full load is, ofcourse, too large for use under conditions of Winter temperatures andpartial loads.

For this reason, the cooling efficiency of air condensing apparatus isregulated in various manners. In the more usual case, a regulatingmethod is employed in which portions of the heat exchange apparatus areoperatively disassociated from the water circulating system. The Waterpresent in the thus disassociated portions of the heat exchangeapparatus is discharged into an appropriate receptacle so as to preventfreezing of the water remaining in the still operating parts of the heatexchanger.

However, the air in that area of the drained heat exchange apparatusnormally occupied by water is above and in contact with the drain pipes,as well as being in contact with the other water which circulates in thestill operating area of the air condensation apparatus or is retainedtherein. The temperature of the water is substantially higher than theair temperature in that area of the drained heat exchanger normallyoccupied by Water. As a'consequence, the air is maintained in a statesaturated With water vapor due to such contact.

As stated, the heat exchangers are usually drained during the coldwinter weather when the air temperature drops below the freezing point,as at this time the heat exchange surface necessary for proper operationis greatly reduced. Thus, both the drained parts of the heat exchangerapparatus and also the walls of the pipes on the water side arenaturally at a temperature below the freezing point.

Under these circumstances, the air in the drained areas of the heatexchange apparatus, and which is saturated with Water vapor, freezes onthe pipe walls, whose temperature is below the freezing point, thusforming an ice coating on these walls. The water vapor thus frozen out,or extracted, from the air, leaves a vacuum which is then filled withfresh water vapor by way of the drain pipes,

dd'l dhd Patented Apr. 20, 1965 so that the air is again saturated withwater-vapor. As a result, a very heavy ice coating or formation willbuild up. If the temperatures remain below the freezing point for anylength of time, thecondition just mentioned will result in the waterpipes of the heat exchange apparatus being frozen completely due to thesteadily increasing thickness of the ice coating thereon.

it frequently happens, in the operation of air condensing equipment,that a previously. drained portion or area of the heat exchangeapparatus must be restored to operation when the ambient temperature isbelow the freezing point. This requires that such drain portion of theheat exchange apparatus, and particularly the Water circulation throughand substantially unimpeded .Water circulation is not achievedsubstantially immediately in all the water circulation system, freezingwill occur in those parts of the circulating system where, for anyreason, the circulation of Water is impeded to any substantial extent.The afore mentioned build-up of ice coatings in part or all of the watercirculating system may impede the water circulation sutliciently, duringthe relatively brief time interval required for freezing of the pipesupon the start of Water flow therethrough, so that the water flow isblocked. It is therefore necessary, in the interest of safety ofoperation of the air condensing equipment, to provide an arrangement forpreventing the formation of such ice coatings in the exhaust aircondensing apparatus.

The present invention is directed to a novel and efiicient arrangementfor preventing the building up ofice coatings in the water circulatingsystems of exhausted air condensing apparatus, and this is the principalobject of the it present invention. More particularly, in accordancewith heat exchange apparatus,'while closing automatically,

after the heat exchange apparatus is drained, to prevent seepage ofwater vapor through the drain pipes back into the heat exchangeapparatus. Thereby the building up of the aforementioned ice layers issubstantially inhibited.

Accordingly, a further object of the invention is to provide, in heatexchange apparatus including air condensing units having watercirculating systems connected by drain pipes to a tank for storage ofdischarged water, a device for inhibiting freezing of the heatexchanging apparatus and comprising air shut-01f valve means in thedrain pipe or pipes between the heat exchange apparatus and the usualdrain shut-01f valves.

A still further object of the invention is to provide such an airshut-off valve means having a primary sealing surface biased to theclosed position and a secondary sealing surface within the primarysealing surface and likewise biased to the closed position and locatedat the lowest point of the primary sealing surface.

Another object ofthe inventionis to provide such an air shut-off valvein which the free cross sectional area of the secondary sealing surfaceor valve does not exceed 4 of the free cross sectional area of theprimary sealing surface or valve.

A further object of the invention is to provide such an.

For an understanding of the principles of the invention, reference ismade to the following description of a typical embodiment thereof asillustrated in the accompanying drawings. In the drawings:

FIG. 1 is a somewhat schematic and diagrammatic elevational view ofapparatus embodying the invention;

FIG. 2 is a plan view, partly in section, of an air shutoff valveembodying the invention;

FIG. 3 is an axial sectional view through the air shutoff valve shown inFIG. 2; and

FIG. 4 is an enlarged partial sectional view illustrating a detail ofFIG. 3.

As shown in FIG. 1, a heat exchanger, such as an air condenser 1, isconnected to a water inlet 3 and a water outlet 4 through water chambers2. Water inlet 3 and water outlet 4 are provided with shut-off devices,such as valves 5 and 6, respectively, by means of which the watercirculation through the air condenser 1 can be discontinued so thelatter may be disconnected from the water circulating system. Drainpipes 7 are connected to the lines connecting inlet 3 and outlet 4 tovalves 5 and 6, respectively, the drain pipes 7 being connected to thelowest points of these linesand discharging into a tank 8 provided inthe drain pipes 7 to drain cooling Water from the unit 1 into thestorage tank 8. In advance of the shut-off valves 9, each drain pipe 7is provided with an air shut-cit valve means embodying the invention andacting to isolate the unit 1 from the water stored in the tank 8.

The detailed construction of the novel air shut-off valves 10 is shownin FIGS. 2, 3 and 4. Referring to these figures, each valve 10 comprisesa pair of generally semicircular flap valves 11 which are pivotallymounted and conjointly provide a valve head or sealing surface ofrelatively large diameter which is biased to the closing and sealingposition by suitable means, illustrated by way of example ascounterweights 12. As best seen in FIG. 3, each valve 11 has a bentshape including an upwardly curved inner or straight edge, so that, inthe closed position, the major portions of the valves 11 slope down-Wardly and inwardly. The biasing means is so provided or adjusted thatonly about one meter of water head is required to open valves 11. Eachvalve 11 has an aperture at its lowest point, each aperture beingcontrolled by a flexible, such as rubber, flap valve 13 which isarranged to open at a pressure of only a few cm. of water head, so as toprovide for drainage of any water remaining above the valves 11 when thelatter have been closed by their biasing means when most of the waterhas been drained.

By the provision of the dual valve arrangements, oriented and biased asshown in the drawings, the desirable result is obtained that, duringdischarge of water from the unit 1 through the drain pipes 7 incommunication therewith, the water is drained almost completely from theunit whereas, on the other hand, the air space of the drained unit ishermetically sealed off from the tank 8 storing the drained water.

The arrangement operates in the follownig manner. While the unit 1 is inservice, the valves 5 and 6 are open so that cooling water may circulatethrough the heat exchanger 1, and the shut-off valves 9 in the drainpipes 7 are closed. When it is desired to disconnect the unit 1 from thesystem, the shut-oif valves 5 and 6 are closed and the drain shut-offvalves 9 are opened. Thereupon,

"the water in the circulating system of unit 1 and in the pipesconnected thereto drains off into tank 8 and, so long as the head ofwater is above the value necessary to open the valves lll, these valvesremain open and the water flows through the now open shut-oif valves 9into the tank 8. As the water is discharged, the water head is graduallyreduced so that, when there is less than about one meter of water columnabove the valves 10, valves 11 close. However, the valves 13 which areprovided at substantially the center of each of the valve elements 11,remain opened due to the still existing water head until the latter hasbeen decreased to a value of .only a few pm. ,At this latter value, thevalves 13 close a and thus hermetically seal off the tank 8 from theunit 1 so as to prevent water vapor flowing from the tank 8 into theunit I.

As stated, in a preferred arrangement of the invention, the drain pipes7 are not connected directly to the unit I but preferably are connectedto headers, such as 14 and 15, to which may be connected several heatexchanger units.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

1. In combination with an apparatus of the type including heat exchangermeans, means for circulating water therethrough, a storage tank fordrained water, a drain pipe connecting a 'water circulating system ofsaid heat exchanger means to said tank, and a drain shut-off valve insaid drain pipe, which is closed during operation of the heat exchangermeans and is opened to drain the heat exchanger means when the latter istaken out of service: a device for preventing freezing of said heatexchanger means when the latter has been drained, said last-named devicecomprising air shut-off valve means in said drain pipe at the side ofsaid drain shut-ofif valve opposite from said tank and said air shut-offvalve means automatically opening in the direction of flow in said drainpipe toward said tank in response to a pressure head, over said airshutotf valve means, greater than a predetermined value; and biasingmeans biasing said air shut-01f valve means to close when the pressurehead in a direction towad said tank is less than said predeterminedvalue.

2. In combination with an apparatus of the type including heat exchangermeans, means for circulating water therethrough, a storage tank fordrained water, a drain pipe connecting a water circulating system ofsaid heat exchanger means to said tank, and a drain shutoff valve insaid drain pipe, which is closed during operation of the heat exchangermeans and is opened to drain the heat exchanger means when the latter istaken out of service: a device for preventing freezing of said heatexchanger means when the latter has been drained, said lastnamed devicecomprising an air shut-off valve in said drain pipe at the side of saiddrain shut-off valve opposite from said tank and including a relativelylarge area primary valve means automatically opening in the direction offlow from said heat exchanger means to said tank whenever the pressurehead in said direction of flow exceeds a first predetermined value,means biasing said primary valve means to close when the pressure headin a direction toward said tank is less than said first predeterminedvalue; said primary valve means having a relatively small aperturetherethrough; a second valve means, having a relatively small area,controlling flow through said aperture and automatically opening in thedirection of flow from said heat exchanger means to said tank, andbiasing means biasing said secondary valve means to close when thepressure head in the direction toward said tank is less than a secondpredetermined value which is substantially less than said firstpredetermined value.

3. The combination claimed in claim 2, in which the flow area of saidaperture does not exceed of the free cross sectional flow area of saidprimary valve element.

4. The combination claimed in claim 2, including counterweight structureforming said means biasing said primary valve element to the closedposition.

5. The combination claimed in claim 2, wherein said aperture is formedat the lowermost portion of said primary valve element.

6. The combination claimed in claim 5, in which said secondary valveelement is a flap valve of flexible material resiliently biased to theclosed position, and located on the underside of said primary valveelement.

7. The cornbintation claimed in claim 2, in which said drain pipe isconnected between said tank and a header connected to said heatexchanger means and constructed and arranged for connection to otherheat exchanger means.

6 References Cited by the Examiner UNITED STATES PATENTS 2,891,773 6/59Heller 16571 X 5 CHARLES SUKALO, Primary Examiner.

1. IN COMBINATION WITH AN APPARATUS OF THE TYPE INCLUDING HEAT EXCHANGERMEANS, MEANS FOR CIRCULATING WATER THERETHROUGH, A STORAGE TANK FORDRAINED WATER, A DRAIN PIPE CONNECTING A WATER CIRCULATING SYSTEM OFSAID HEAT EXCHANGE MEANS TO SAID TANK, AND A DRAIN SHUT-OFF VALVE INSAID DRAIN PIPE, WHICH IS CLOSED DURING OPERATION OF THE HEAT EXCHANGERMEANS AND IS OPENED TO DRAIN THE HEAT EXCHANGER MEANS WHEN THE LATTER ISTAKEN OUT OF SEVICE: A DEVICE FOR PREVENTING FREEZING OF SAID HEATEXCHANGER MEANS WHEN THE LATTER HAS BEEN DRAINED, SAID LAST-NAMED DEVICECOMPRISING AIR SHUT-OFF VALVE MEANS IN SAID DRAIN PIPE AT THE SIDE OFSAID DRAIN SHUT-OFF VALVE OPPOSITE FROM SAID TANK AND SAID AIR SHUT-OFFVALVE MEANS AUTOMATICALLY OPENING IN THE DIRECTION OF FLOW IN SAID DRAINPIPE TOWARD SAID TANK IN RESPONSE TO A PRESSURE HEAD, OVER SAID AIRSHUTOFF VALVE MEANS, GREATER THAN A PREDETERMINED VALUE; AND BIASINGMEANS BIASING SAID AIR SHUT-OFF VALVE MEANS